As mobile devices have been increasingly developed, and the demand of such mobile devices has increased, the demand of secondary batteries has also sharply increased as an energy source for the mobile devices. Also, much research on batteries satisfying various needs has been carried out.
In terms of the material for the battery, the demand of a lithium secondary battery, such as a lithium cobalt polymer battery, having high energy density, high discharge voltage, and high output stability, is very high. In terms of the shape of the battery, the demand of a rectangular battery or a pouch-shaped battery, which is thin enough to be applied to products, such as mobile phones, and can be stacked with high integration sufficient to be used as a battery for battery modules, is very high. Especially, the pouch-shaped battery is very light and can be manufactured with low costs, and therefore, the pouch-shaped battery is widely used as an energy source for medium- or large-sized devices as well as small-sized mobile devices.
In spite of the above-described advantages, however, the pouch-shaped battery has the following several problems when the pouch-shaped battery is used as the battery for battery modules.
Specifically, the pouch-shaped battery has plate-shaped electrode terminals, which protrude outward from one end of the battery. For this reason, it is difficult to accomplish an electrical connection when a battery module is manufactured using the pouch-shaped battery. Generally, the connection of the electrode terminals is accomplished by welding the corresponding electrode terminals using wires, plates, or bus bars, or by connecting the corresponding electrode terminals using a spring force or another pressure. However, it is difficult to apply the above-described connection methods to the plate-shaped electrode terminals. Generally, the plate-shaped electrode terminals are partially bent such that each plate-shaped electrode terminal has a surface perpendicular to the battery, and the plates or the bus bars are welded to the perpendicular surfaces of the plate-shaped electrode terminals, which requires skilled techniques, and makes a manufacturing process complicated. Furthermore, the pouch-shaped battery has low mechanical strength, and therefore, the coupled regions are easily separated from each other due to external impacts, which may lead to defectiveness of the pouch-shaped battery.
Also, a plurality of additional members for maintaining stable coupling and assembly of a plurality of batteries are needed when the plurality of batteries are stacked one on another so as to manufacture a battery module. When a battery module is manufactured using the pouch-shaped battery, additional mounting members, such as cartridges, are used to manufacture the battery module. However, the use of the mounting members makes the assembly process of the battery module complicated and further increases the overall size of the battery module.
Another method of interconnecting the plate-shaped electrode terminals is disposed in Korean Patent Application No. 2004-112592, which has been filed in the name of the applicant of the present patent application. According to the disclosure of the above-mentioned patent application, through-holes are formed through a plurality of electrode terminals, and an additional connecting member is inserted through the through-holes, whereby the interconnection between the plate-shaped electrode terminals is accomplished. In the above-described conventional interconnecting method, however, the contacting forces between the through-holes and the connecting member are different for the respective unit cells, which changes the resistance of the battery. In addition, the plate-shaped structure, which has low mechanical strength, is used as an assembly means.